1. Field of the Invention
The present invention relates generally to a microparticle sampler and more particularly, to a portable nanoparticle (NP) sampler.
2. Description of the Related Art
According to many studies, inhaled NPs pose a high adverse effect on human health. To assess the occupational health risk due to the exposure to the NPs in workplaces, it is necessary to collect the NPs of various diameters for further analysis of their ingredients.
A variety of NP samplers have been commercially available, including electric low-pressure impactor (ELPI), low-pressure impactor (LPI), microorifice uniform deposition impactor (MOUDI), and nano micro-orifice uniform deposition impactor (Nano-MOUDI). However, such samplers are too large and too heavy. Besides, the flow rate and the pressure loss are too high in the process of sampling to make the samplers work with small portable pumps. Thus, they could only be put at a fixed location for collecting NPs.
To measure the particle concentration at the actual workplaces more accurately, the inventors of the present invention successfully developed a personal NP sampler as disclosed in U.S. Pat. Laid-open No. 2009/0272202. The personal NP sampler is composed of a per-classifier, a nozzle, a particle-sizing filter pack, and a final filter pack from bottom to top for guiding an airflow from bottom to top to enable the airflow to be filtered by a particle-sizing filter and the final filter. Although such personal NP sampler can collect the NPs of different diameters via two stages and be applied to the small pump, the cutoff diameter of the particle-sizing filter is related to the flow rate of the airflow thereat and the flow rate is subject to the invariable number of the pores of the particle-sizing filter in such a way that a deviation happens between the cutoff diameter thereat and the default.
In other words, the aforesaid personal NP sampler though has had preferable portability but the cutoff diameter is subject to slight inaccuracy, so it still needs further improvement.